Vibration based power generator

ABSTRACT

A vibration based power generator. In a described embodiment, an electrical power generating system includes a vibrating assembly including a vortex shedding device which sheds vortices in response to fluid flow across the vibrating assembly. A generator generates electrical power in response to vibration of the vibrating assembly. The vortex shedding device sheds the vortices at a frequency which is substantially equal to a resonant frequency of the vibrating assembly.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is related to copending application Ser. No.10/825,350, the entire disclosure of which is incorporated herein bythis reference.

BACKGROUND

The present invention relates generally to electrical power generationand, in an embodiment described herein, more particularly provides avibration based power generator.

It is well known in the art to produce electrical power from vibrationof a member or assembly due to fluid flow impinging on the member orassembly. However, past designs of such vibration based power generatorshave not achieved maximum efficiency in coupling the fluid flow to thevibrating member or assembly. Consequently, most prior vibration basedpower generators do not most effectively utilize energy available in thefluid flow for conversion to electricity.

Furthermore, some prior vibration based power generators unacceptablyobstruct a passage through which the fluid flows. This creates apressure drop in the passage and restricts access through the passage.

From the foregoing, it can be seen that it would be quite desirable toprovide an improved vibration based power generator.

SUMMARY

In carrying out the principles of the present invention, in accordancewith an embodiment thereof, an electrical power generating system isprovided which efficiently converts fluid flow energy into electricalenergy without substantially obstructing fluid flow or access throughthe system.

In one aspect of the invention, an electrical power generating system isprovided which includes an elongated arm having a vortex shedding deviceat one end and an electrical power generator at an opposite end of thearm. An elastic support supports the arm against alternating lift forcesproduced by vortices shed by the vortex shedding device.

In another aspect of the invention, an electrical power generatingsystem is provided which includes a vibrating assembly including avortex shedding device which sheds vortices in response to fluid flowacross the vibrating assembly. A generator generates electrical power inresponse to vibration of the vibrating assembly. The vortex sheddingdevice sheds the vortices at a frequency which is substantially equal toa resonant frequency of the vibrating assembly.

These and other features, advantages, benefits and objects of thepresent invention will become apparent to one of ordinary skill in theart upon careful consideration of the detailed description ofrepresentative embodiments of the invention hereinbelow and theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic partially cross-sectional view of a well whichincludes an electrical power generating system embodying principles ofthe present invention;

FIG. 2 is side view of a first electrical power generating systemembodying principles of the present invention which may be used in thewell of FIG. 1;

FIG. 3 is another side view of the system of FIG. 2, rotated 90 degreesabout its longitudinal axis;

FIGS. 4A–D are side views of alternate configurations of vortex-sheddingdevices which may be used in the system of FIGS. 2 & 3;

FIG. 5 is graph of vortex shedding frequency versus flow velocity in thesystem of FIGS. 2 & 3;

FIG. 6 is an isometric view of a second electrical power generatingsystem embodying principles of the present invention;

FIG. 7 is an isometric view of a third electrical power generatingsystem embodying principles of the present invention;

FIG. 8 is an isometric view of an elastic support and electrical powergenerator which may be used in the system of FIG. 7;

FIG. 9 is an isometric view of a lever device which may be used in thesystem of FIG. 7;

FIG. 10 is a partially cross-sectional view of a fourth electrical powergenerating system embodying principles of the present invention;

FIG. 11 is a partially cross-sectional view of a fifth electrical powergenerating system embodying principles of the present invention;

FIG. 12 is a partially cross-sectional view of a portion of the fifthsystem, taken along line 12—12 of FIG. 11;

FIG. 13 is a partially cross-sectional view of a sixth electrical powergenerating system embodying principles of the present invention;

FIG. 14 is a partially cross-sectional view of a seventh electricalpower generating system embodying principles of the present invention;

FIG. 15 is a partially cross-sectional view of an eighth electricalpower generating system embodying principles of the present invention;

FIG. 16 is a partially cross-sectional view of a ninth electrical powergenerating system embodying principles of the present invention;

FIG. 17 is a partially cross-sectional view of a tenth electrical powergenerating system embodying principles of the present invention;

FIG. 18 is a partially cross-sectional view of an eleventh electricalpower generating system embodying principles of the present invention;

FIG. 19 is a partially cross-sectional view of a twelfth electricalpower generating system embodying principles of the present invention;

FIG. 20 is a schematic view of a magnet configuration which may be usedin electrical power generating systems embodying principles of thepresent invention;

FIG. 21 is a partially cross-sectional view of a thirteenth electricalpower generating system embodying principles of the present invention;

FIG. 22 is a plot of lift coefficient versus angle of attack for thethirteenth system of FIG. 21;

FIG. 23 is a partially cross-sectional view of a fourteenth electricalpower generating system embodying principles of the present invention;

FIG. 24 is a schematic view of a fifteenth electrical power generatingsystem embodying principles of the present invention;

FIG. 25 is a schematic view of a sixteenth electrical power generatingsystem embodying principles of the present invention;

FIG. 26 is a schematic view of an alternate configuration of thefifteenth electrical power generating system; and

FIG. 27 is a schematic view of an alternate configuration of thesixteenth electrical power generating system.

DETAILED DESCRIPTION

Representatively illustrated in FIG. 1 is a configuration of asubterranean well 10 which embodies principles of the present invention.In the following description of the well 10 and other apparatus andmethods described herein, directional terms, such as “above”, “below”,“upper”, “lower”, etc., are used only for convenience in referring tothe accompanying drawings. Additionally, it is to be understood that thevarious embodiments of the present invention described herein may beutilized in various orientations, such as inclined, inverted,horizontal, vertical, etc., and in various configurations, withoutdeparting from the principles of the present invention.

The well 10 is described herein as being a producing well in which fluidis produced from a formation 12 into a tubular string 14, and is thenflowed through the tubular string to the earth's surface. However, it isto be clearly understood that principles of the present invention may beincorporated into other types of wells and other systems, for example,where fluid is injected into a formation or circulated in the well (suchas during drilling operations), where fluids pass from a relatively highpressure source to a relatively low pressure zone within the well, orwhere fluid flows from a pump or other “artificial” pressure source,etc. Thus, it is not necessary in keeping with the principles of thepresent invention for fluid to be produced through a tubular string orfrom a well.

In the well 10 as depicted in FIG. 1, fluid from the formation 12 entersthe tubular string 14 through a valve 16 or other opening in the tubularstring and flows upwardly in the tubular string. Interconnected in thetubular string 14 is an electrical power generating system 18 throughwhich the fluid flows. In one important aspect of the present invention,this fluid flow through the system 18 causes it to generate electricalpower. This electrical power may then be used to operate a downholetool, such as a valve 20 interconnected in the tubular string 14. It isto be clearly understood that the valve 20 is used merely as an exampleof the wide variety of downhole tools and other types of devices thatmay be powered by the system 18, such as sensors, samplers, flow controldevices, communication devices, etc.

Electric lines or conductors 22 may be used to electrically connect thesystem 18 to the valve 20, enabling the valve to be remotely locatedrelative to the system. Alternatively, the system 18 and valve 20 (orother downhole tools or other devices) may be integrally formed ordirectly connected to each other. Furthermore, the system 18 may bepositioned above or below the valve 20, or in any other positionrelative to the valve.

Referring additionally now to FIG. 2, internal components of the system18 are representatively illustrated apart from the remainder of thesystem and the well 10. Specifically, a vibrating assembly 156 includinga vortex shedding device 24 and an elongated beam or arm 26, an elasticsupport 28 and an electrical power generator 30 are schematicallydepicted in FIG. 2.

Fluid flow through the system 18 is represented by arrows 32. The fluidflow 32 impinges on the vortex shedding device 24, thereby causingelectrical power to be generated by the generator 30. The fluid flow 32may include one or more liquids (such as oil, water, etc.), one or moregases (such as natural gas, nitrogen, air, etc.), one or more solids(such as sand, mud, etc.) or any combination of liquid, gas and/orsolid.

When the fluid flow 32 does not impinge on the device 24, the device andarm 26 are maintained in a neutral position by the elastic support 28.However, when the fluid flow 32 impinges on the device 24, the devicesheds vortices 34 which produce alternating lift forces 36 on the deviceand the arm 26, causing the device and arm to vibrate. These vortices 34and lift forces 36 are representatively illustrated in FIG. 3, whichdepicts a side view of the system 18 rotated 90 degrees from that shownin FIG. 2.

In FIG. 3 it may be seen that the vortices 34 shed by the device 24impinge on lateral surface areas 38 of the device, and on lateralsurface areas 40 of the arm 26. The lift forces 36 produced by thevortices 34 impinging on the surface areas 38, 40 cause the arm 26 anddevice 24 to displace laterally back and forth, as represented by arrows42. Note, however, that vibrations and displacements other thanlaterally directed (such as rotational or axial displacements, etc.)could be used in keeping with the principles of the invention.

The frequency of this back and forth vibration or displacement 42 of thearm 26 and device 24 is determined in substantial part by the stiffnessor rigidity of the elastic support 28, since displacement of the armproduces strain in the elastic support. Preferably, the arm 26 anddevice 38 are very rigid, so that only minimal strain is imparted tothese elements by the lift forces 36 due to the shed vortices 34.However, the arm 26 and/or device 38 could be made more flexible if, forexample, it is desired to modify a resonant frequency or amplitude atwhich the displacement 42 occurs, reduced stiffness in these elements isused to enhance the efficiency of the system 18, etc.

The vibrating displacement 42 of the arm 26 is converted intoelectricity by the generator 30. The generator 30 may be any type ofdevice which is capable of converting the displacement 42 intoelectricity. Several embodiments of the generator 30 are describedbelow, but it should be clearly understood that the principles of theinvention are not limited to any particular embodiment or method ofgenerating electricity described herein.

The frequency and amplitude of the vibrating displacement 42 aregoverned by several factors, including the mass, location and relativestiffness of each displacing element of the system 18. Preferably, theelastic support 28 is less rigid than the arm 26, so that the arm is notsubstantially flexed or bent along its length during the displacement42. The elastic support 28 biases the arm 26 toward its neutral positionwhen the lift forces 36 due to the vortices 34 displace the arm awayfrom the neutral position. In general, the more rigid the elasticsupport 28, the greater the resonant frequency of the assembly 156.

The vortices 34 are shed and impinge on the device 24 and arm 26 at afrequency which is dependent in substantial part on the velocity of thefluid flow 32. In general, as the velocity of the fluid flow 32increases, the frequency of the vortices 34 also increases. As explainedin more detail below, the frequency at which the vortices 34 are shed ispreferably substantially equal to the resonant frequency of the assembly156, so that the lift forces 36 produced by the vortices enhance theamplitude of the displacement 42, thereby increasing the level ofelectrical power produced by the generator 30.

Referring additionally now to FIGS. 4A–D, several different alternateconfigurations 44, 46, 48, 50 of the vortex shedding device 24 arerepresentatively illustrated. It should be clearly understood that thevortex shedding device 24 is not limited to these configurations 44, 46,48, 50. Instead, any configuration of the vortex shedding device 24 maybe used in keeping with the principles of the invention.

Each of the configurations 44, 46, 48, 50 presents a substantially flatplanar face 52 to the fluid flow 32. Accordingly, such vortex sheddingdevices may be known to those skilled in the art as “bluff” bodies.Alternatively, the face 52 could be rounded, concave, convex, orotherwise shaped, without departing from the principles of theinvention.

The vortices 34 are shed as the fluid flow 32 spills over the edges ofthe face 52. The configurations 44, 46, 48, 50 differ most substantiallyin how they are shaped downstream of the face 52, which influences thefrequency at which the vortices 34 are shed and how the vortices impingeon lateral sides of the respective configurations.

The configuration 48 depicted in FIG. 4C is presently preferred for thevortex shedding device 24. This is due in substantial part to: 1) itsrelatively sharp edge 54 formed around the face 52, which enables it toreadily shed vortices 34 at relatively low velocities of the fluid flow32; 2) its relatively uncomplicated shape, which makes it inexpensive tomanufacture and reproduce with precision; and 3) its relatively largeand flat lateral surface areas 56 downstream of the face 52, whichenhance the lift forces produced when vortices shed by the deviceimpinge on these surface areas.

Referring additionally now to FIG. 5, a graph of vortex sheddingfrequency (f) versus flow velocity (U) in the system 18 isrepresentatively illustrated. A solid line 58 on the graph indicates atheoretical proportional relationship between the vortex sheddingfrequency (f) and the flow velocity (U) as predicted by the followingequation:St=(fD)/U   (1)where St is a coefficient known as the Strouhal number, and D is acharacteristic dimension of the vortex shedding device. For subterraneanwell applications using the system 18, in which the fluid flow 32 wouldlikely have a Reynolds number of approximately 10² to approximately 10⁵,the Strouhal number is expected to be approximately 0.1 to approximately0.2. For the preferred vortex shedding device configurations 44, 46, 48,50 described above, the characteristic dimension D may be a width of theface 52.

However, due to a phenomenon known to those skilled in the art as “lockin,” the relationship between the vortex shedding frequency (f) and thefluid flow velocity (U) in the system 18 is not directly proportionalfor all flow velocities as described by the line 58. Instead, as thevortex shedding frequency (f) approaches the resonant frequency(represented by the horizontal dotted line 60 in FIG. 5) of thevibrating assembly 156, the vortex shedding frequency locks in (remainsrelatively constant) over a range of fluid flow velocity (U). This isdepicted by the alternating dotted and dashed line 62 in FIG. 5, whichhas a substantially horizontal portion 64 indicating that, for a rangeof fluid flow velocity (U), the vortex shedding frequency (f) remainssubstantially constant at the resonant frequency 60 of the assembly 156.

Thus, the system 18 is preferably configured so that, at an expected orpredetermined range of fluid flow velocity (U) through the system, itsvortex shedding frequency (f) is substantially equal to the resonantfrequency 60 of the assembly 156. The vortex shedding frequency (f) ofthe system 18 at a predetermined fluid flow velocity (U) may be adjustedby, for example, varying the characteristic dimension D in equation (1)above. The resonant frequency 60 of the assembly 156 may be adjusted by,for example, varying the rigidity of the arm 26 and/or elastic support28, varying the length of the arm, varying the mass of the arm and themass of the vortex shedding device 24, etc.

Referring additionally now to FIG. 6, internal components of anotherelectrical power generating system 70 are representatively illustrated.The system 70 may be used for the system 18 in the well 10 asillustrated in FIG. 1, or it may be used in other applications.

The system 70 includes a vibrating assembly 158 which comprises a vortexshedding device 72 attached at one end of an arm 74. An electrical powergenerator 76 is attached at an opposite end of the arm 74. An elasticsupport 78 is attached to the arm 74 between the device 72 and thegenerator 76.

The vortex shedding device 72 is shaped somewhat like the configuration46 depicted in FIG. 4B. The elastic support 78 has a generally I-shapedcross-section which permits rotational displacement (indicated by arrows80) of the arm 74 about the support. The arm 74 is preferablysubstantially more rigid than the elastic support 78, so that onlyminimal flexing of the arm occurs during the vibrating displacement 80.

The generator 76 includes two permanent magnets 82 attached to the arm74, and two corresponding stationary wire coils 84. Electricity isproduced from the coils 84 when the magnets 82 are displaced in thecoils due to the vibrating displacement 80 of the arm 74. Of course, anynumber of magnets 82 and coils 84 may be used, the magnets and coils maybe differently configured or oriented, etc.

The magnets 82 and coils 84 may be used to produce an initialdisplacement of the arm 74, if desired. As described more fully below,an electric potential may be applied to one or both of the coils 84 togenerate a magnetic field and thereby bias the magnets 82 to displaceagainst the biasing force exerted by the elastic support 78. This willdisplace the arm 74 away from its neutral position and help to initiatethe vibrating displacement 80 of the vibrating assembly 158.

Referring additionally now to FIG. 7, components of another electricalpower generating system 86 are representatively illustrated. The system86 may be used for the system 18 in the well 10 as illustrated in FIG.1, or it may be used in other applications.

The system 86 includes a vibrating assembly 160 which comprises an arm88 and a vortex shedding device 90 attached to a combined elasticsupport and generator 92. The vortex shedding device 90 is attached atone end of the arm 88, and two of the support and generator 92 areattached at an opposite end of the arm. The vortex shedding device 90 issimilar to the configuration 48 depicted in FIG. 4C.

The support and generator 92 is similar in many respects to an actuatordescribed in U.S. Pat. No. 5,907,211, the entire disclosure of which isincorporated herein by this reference. As described in that patent, theactuator uses stacks of piezoelectric elements and a leveragingmechanism. When an electric potential is applied to the piezoelectricelements, the elements deform, and this deformation is amplified by theleveraging mechanism so that a relatively large stroke is produced bythe actuator. In the support and generator 92 of the system 86, however,electricity is produced (instead of being applied to the piezoelectricelements), and the leveraging mechanism reduces displacement (instead ofamplifying displacement).

The support and generator 92 is depicted in FIG. 8 apart from theremainder of the system 86. In this view it may be seen that the supportand generator 92 includes two stacks of electromagnetically activeelements 94 positioned within a leveraging mechanism 96. A pivot 98 isat one end of the leveraging mechanism 96. An opposite end of theleveraging mechanism 96 has attachment portions 100 formed thereon. Inthe system 86 as depicted in FIG. 7, one of the attachment portions 100is secured to the arm 88, and the other of the attachment portions 100is attached to a generally tubular housing 102.

As the arm 88 vibrates (due to the fluid flow 32 through an internalpassage 104 formed through the housing 102, and the resulting vortices34 shed from the vortex shedding device go), it rotates back and forthabout a pivot 106 supporting the arm between the vortex shedding deviceand the two supports and generators 92. This vibrating displacement ofthe arm 88 is transmitted to the supports and generators 92 via theattachment portions 100. The vibrating displacement of the arm 88transmitted to the supports and generators 92 causes strain to beinduced in the elements 94 by the leveraging mechanisms 96.

The leveraging mechanisms 96 decrease the displacement of the arm 88 asapplied to the elements 94, in order to achieve a better mechanicalimpedance match to the electromagnetically active material. The biasingforces produced by the flow-induced vibration tend to behave like a softspring while many of the electromagnetically active materials behavelike a hard spring. The leveraging mechanisms 96 allow more of theflow-induced energy to enter the electromagnetically active elements 94.

As described above, the elements 94 are electromagnetically activeelements. The term “electromagnetically active” as used herein indicatesa material which produces an electric potential and/or current(electro-active material), or a magnetic field (magneto-activematerial), when the material is subjected to strain. Examples ofelectromagnetically active materials include piezoelectrics (includingpiezo-ceramics, piezo-polymers, etc.), magnetostrictors andelectrostrictors.

If the elements 94 are made of magnetostrictive material which producesa magnetic field when strained, then at least one wire coil (such as acoil 84) may be included in the supports and generators 92, so that themagnetic field will produce electricity in the coil. If the elements 94are made of piezoelectric or electrostrictive material, then electricityis produced directly from the material when it is strained.

Preferably, the elements 94 are made of a piezoelectric material, arestacked in series as depicted in FIG. 8, and are electrically connectedin parallel. As illustrated in FIG. 8, conductors 22 are connected tothe elements 94 for providing electrical power to the well tool 20 asdepicted in FIG. 1.

The supports and generators 92 also provide support for the arm 88. Thesupports and generators 92 bias the arm 88 toward a neutral position,due to the overall elasticity of the elements 94 and leveragingmechanism 96. If desired, a preload may be applied to the supports andgenerators 92, so that vibrating displacement of the arm 88 is mosteffectively transmitted to the elements 94 via the leveraging mechanisms96, and so that the arm is retained at its neutral position when thefluid flow 32 is not sufficient to cause the arm to vibrate. The preloadmay be applied to maintain a compressive load on the elements 94 inorder to reduce tensile fracture of the elements.

To produce an initial displacement of the arm 88, one or both of thesupports and generators 92 may be used for its/their actuatorcapability. That is, an electric potential or magnetic field may beapplied to the elements 94, thereby producing strain in the elements andcausing the arm 88 to deflect in a desired direction. In this manner, aninitial displacement of the arm 88 may be produced to initiate thevibrating displacement of the vibrating assembly 160 in response to thefluid flow 32.

Referring additionally now to FIG. 9, a lever device 110 isrepresentatively illustrated. The lever device 110 may be used in theleveraging mechanism 96 in the support and generator 92. However, itshould be clearly understood that the lever device 110 may be used inother mechanisms, devices and systems, in keeping with the principles ofthe invention.

Instead of the pivot 98 positioned at one end of substantially rigidmembers 154 (as depicted for the leveraging mechanism 96 in FIG. 8), thelever device 110 has flexure pivots 112 formed directly on a singlepiece of material. Thus, the lever device 110 may be used in place ofthe members 154 and pivot 98 in the leveraging mechanism 96.

The flexure pivots 112 are formed as relatively thin portions of thematerial, and are positioned closer to the attachments 100 than in theleveraging mechanism 96 as depicted in FIG. 8, giving a differentmechanical ratio for transmitting displacement of the arm 88 to theelements 94. Integrally forming the lever device 110 from a single pieceof material reduces the cost and complexity of the leveraging mechanism96.

The pivot 106 may also be considered a part of the support for the arm88. The pivot 106 attaches the arm 88 to the housing 102. The pivot 106may also include one or more elastic elements which bias the arm 88toward its neutral position.

As depicted in FIG. 7, the arm 88 and vortex shedding device 90 arepositioned in a recess 108 formed in a sidewall of the housing 102.Although the recess 108 is shown in FIG. 7 as being open to an exteriorof the housing 102, in actual practice a covering is preferablyinstalled over the recess so that the fluid flow 32 is contained withinthe housing.

By positioning the arm 88 and vortex shedding device 90 in the recess108, the passage 104 remains substantially unobstructed. This minimizesany pressure drop in the fluid flow 32 though the system 86, whileproviding access for wireline tools, coiled tubing, etc. through thepassage 104. Note that some or all of the vortex shedding device 90and/or arm 88 may extend into the passage 104, in keeping with theprinciples of the invention.

Although being positioned in the recess 108, the arm 88 and vortexshedding device 90 are still exposed to the fluid flow 32 through thepassage 104. The arm 88 is preferably positioned at an outer portion ofthe recess 108, however, so that it is exposed in large part only toboundary layer flow in the recess. This minimizes energy losses due toexposure of the arm 88 to the fluid flow 32.

The vortex shedding device 90 may be positioned so that a portion of thedevice extends into the passage 104. This exposes the vortex sheddingdevice 90 to higher velocity fluid flow 32 in the passage 104, withoutsubstantially obstructing the passage.

Referring additionally now to FIG. 10, another electrical powergenerating system 114 is representatively illustrated. The system 114demonstrates that various techniques may be used to increase thevelocity of the fluid flow 32 which impinges on a vortex shedding devicein a recess laterally offset from a passage.

The system 114 may be used for the system 18 in the well 10 asillustrated in FIG. 1, or it may be used in other applications. Thesystem 114 includes features which enhance exposure of a vortex sheddingdevice 116 to the fluid flow 32 through a passage 118 formed through ahousing 120.

A vibrating assembly 162 of the system 114 includes the vortex sheddingdevice 116 attached to an end of an arm 122. An opposite end of the arm122 is attached to an elastic support 124 and an electrical generator126. The elastic support 124 and generator 126 may be similar to any ofthe supports and generators described above, or other types of supportsand generators may be used if desired.

The vortex shedding device 116 and arm 122 are positioned in a recess128 formed in a sidewall of the housing 120 laterally offset from thepassage 118. Since the recess 128 is in communication with the passage118 along its entire length, the vortex shedding device 116 is alsoexposed to the fluid flow 32 through the passage 118.

To increase the velocity of the fluid flow 32 impinging on the vortexshedding device 116, upstream and downstream surfaces 130, 132 of therecess 128 are inclined relative to a longitudinal axis of the passage118 at an angle (a) substantially less than 90 degrees. This provides agradual transition for the fluid flow 32 between the passage 118 and therecess 128, thereby reducing turbulence in the flow and increasing thevelocity of the flow in the recess.

To enhance diversion of the fluid flow 32 toward the recess 128, a flowdiverter 140 including a series of longitudinally spaced apart andcircumferentially extending projections 134 is formed in the housing120. The projections 134 extend into the passage 118, but not into therecess 128. In this manner, flow through the passage 118 is somewhatrestricted, thereby diverting more of the fluid flow 32 toward therecess 128 and increasing the velocity of the fluid flow in the recess.

Other means of diverting the fluid flow 32 toward the recess 128 may beused, including those described in U.S. patent application Ser. No.10/658,899, entitled BOREHOLE DISCONTINUITIES FOR ENHANCED POWERGENERATION, filed Sep. 10, 2003, the entire disclosure of which isincorporated herein by this reference.

Note that the arm 122 is positioned in a portion of the recess 128 nearits outermost extent and relatively close to the housing 120 sidewall.This positioning of the arm 122 places it substantially in a boundarylayer of the fluid flow 32 in the recess 128, or at least in a region ofreduced flow and turbulence, thus reducing energy lost due todisplacement of the arm in the fluid.

Referring additionally now to FIG. 11, another electrical powergenerating system 136 is representatively illustrated. The system 136 issimilar in many respects to the system 114 described above, and soelements depicted in FIG. 11 which are similar to those described aboveare indicated using the same reference numbers. The system 136 may beused for the system 18 in the well 10 as illustrated in FIG. 1, or itmay be used in other applications.

The system 136 differs from the system 114 in one respect in that,instead of the recess 128, the system 136 includes a channel 138 whichis laterally offset from the passage 118. The channel 138 is preferablyformed in a sidewall of the housing 142 and is separated from thepassage by a wall 144. However, opposite ends of the channel 138 are influid communication with the passage 118, so that the fluid flow 32 maypass from the passage 118 into the channel 138 and back to the passage.The wall 144 serves to protect the vortex shedding device 116 and arm122 from debris, tools, etc. which may pass through the passage 118.

The system 136 also differs from the system 114 in another respect inthat, instead of the projections 134, the system 136 has a flow diverter146 which includes a pivotably mounted vane 148. A biasing device 150,such as a spring, biases the vane 148 to restrict flow through thepassage 118 at the wall 144 as depicted in FIG. 11, thereby divertingthe fluid flow 32 toward the channel 138. If at some point it is desiredto provide access to the passage 118 below the vane 148, the vane may berotated out of the way (counterclockwise as depicted in FIG. 11) againstthe biasing force exerted by the biasing device 150.

Referring additionally now to FIG. 12, a side view of the system 136 isrepresentatively illustrated, taken along line 12—12 of FIG. 11. In thisview another method of increasing the velocity of the fluid flow 32impinging on the vortex shedding device 116 in the channel 138 isillustrated.

Specifically, a flow diverter 152 is positioned in the channel 138upstream of the vortex shedding device 116. Preferably, the diverter 152is positioned upstream from the vortex shedding device 116 a distancesomewhat less than the width of the face of the vortex shedding device,and the diverter blocks about half of the flow area of the channel 138.By reducing the flow area of the channel 138 just upstream of the vortexshedding device 116, the velocity of the fluid flow 32 impinging on thevortex shedding device is increased.

In addition, the diverter 152 causes the fluid flow 32 to impinge on thevortex shedding device 116 at an angle (A) relative to the longitudinalaxis of the passage 118. Preferably, the angle (A) is substantiallygreater than zero and is in the range of approximately 20 degrees toapproximately 60 degrees. This angular impingement of the fluid flow 32on the vortex shedding device 116 may enhance initiation of vibratingdisplacement of the assembly 162. Note that the diverter 152 may also,or alternatively, be used in the recess 108 in the system 86 upstream ofthe vortex shedding device go, and in the recess 128 in the system 114upstream of the vortex shedding device 116.

Referring additionally now to FIG. 13, another electrical powergenerating system 164 is representatively illustrated. The system 164 issimilar in many respects to the system 70 described above (see FIG. 6),and so elements depicted in FIG. 13 which are similar to those describedabove are indicated using the same reference numbers. The system 164 maybe used for the system 18 in the well 10 as illustrated in FIG. 1, or itmay be used in other applications.

The system 164 differs from the system 70 in one respect in that agenerator 166 of the system includes two stacks of electromagneticallyactive elements 168 positioned within the two coils 84. Each stack ofelectromagnetically active elements 168 is also positioned between oneof the magnets 82 and an outer generally tubular housing 170 having apassage 172 through which the fluid flow 32 passes.

As the vibrating assembly 158 displaces (as indicated by arrows 80),strain is produced in the elements 168, thereby generating either amagnetic field (e.g., if the elements are made of magnetostrictivematerial) which produces electricity in the coils 84, or generatingelectricity in the elements (e.g., if the elements are made ofpiezoelectric or electrostrictive material). Thus, electricity isproduced from the strain in the elements 168, in addition to electricitybeing produced due to displacement of the magnets 82 relative to thecoils 84 (which will be relatively minimal compared to that produced dueto strain in the elements 168).

Furthermore, the magnets 82 provide a magnetic bias on the elements 168(if the elements are made of a magnetostrictive material) whichincreases the magnetic flux produced due to a given strain.

Preferably, the elements 168 are stacked in series and are electricallyconnected in parallel (if the elements are made of piezoelectric orelectrostrictive material). Note that the elements 168 (and associatedcoil 84, if the elements are made of magnetostrictive material) may beused in any of the electrical power generating systems described herein,in order to produce electricity from displacement of the vibratingassembly in each system. Note, also, that it is not necessary for themagnets 82 to be provided in the system 164, since strain in theelements 168 can be used to produce electricity without use of themagnets.

Referring additionally now to FIG. 14, another electrical powergenerating system 174 is representatively illustrated. The system 174 issimilar in many respects to the system 164 described above, and soelements depicted in FIG. 14 which are similar to those described aboveare indicated using the same reference numbers. The system 174 may beused for the system 18 in the well 10 as illustrated in FIG. 1, or itmay be used in other applications.

The system 174 differs from the system 164 in one respect in that itincludes one magnet 82 attached to the arm 74. The magnet 82 isdisplaced relative to the coil 84 when the vibrating assembly 158displaces in response to the fluid flow 32. The coil 84 is substantiallyrigidly mounted relative to the housing 170. Of course, other numbers ofmagnets 82 and coils 84 may be used, and the coil 84 could be displacedby the vibrating assembly 158 while the magnet 82 remains rigidlymounted, without departing from the principles of the invention.

One beneficial feature of the system 174 is that a passage 176 formedthrough the coil 84 is in fluid communication with the passage 172formed through the housing 170 at each opposite end of the coil. Themagnet 82 displaces in the passage 176 when the vibrating assembly 158displaces. This configuration helps to prevent accumulation of debriswithin the coil 84. An additional benefit of the system 174 is that thespeed with which the magnet 82 displaces through the coil 84 isincreased (due to a decreased mass), which increases the rate ofmagnetic flux change, and as a result leads to higher generatedvoltages.

In addition, each of the magnet 82 and coil 84 is preferably alignedwith a longitudinal axis 178 of the vibrating assembly 158, whichprovides for reduced obstruction of the passage 172. Of course, thesystem 174, as well as each of the other systems described herein, maybe positioned in a laterally offset recess or channel (as describedabove and illustrated in FIGS. 10–12) to further reduce obstruction tothe fluid flow 32 and enhance access through the passage 172.

Referring additionally now to FIG. 15, another electrical powergenerating system 180 is representatively illustrated. The system 180 issimilar in many respects to the system 174 described above, and soelements depicted in FIG. 15 which are similar to those described aboveare indicated using the same reference numbers. The system 180 may beused for the system 18 in the well 10 as illustrated in FIG. 1, or itmay be used in other applications.

The system 180 differs from the system 174 in one respect in that,instead of displacing the magnet 82 in the passage 176 of the coil 84,the magnet is displaced relative to a ferromagnetic core 182 in thecoil. Of course, the coil 84 and core 182 could be displaced relative tothe magnet 82, and multiple coils, cores and magnets could be used, inkeeping with the principles of the invention.

The ferromagnetic core 182 could be made of materials such as steel,nickel, etc., or any other material capable of directing magnetic fluxfrom the magnet 82 through the coil 84. As the magnet 82 displacesrelative to the core 182, the magnetic flux density in the core (and,thus, in the coil 84) changes, thereby producing electricity in thecoil.

One beneficial feature of the system 180 is that the core 182 preventsdebris from entering the coil 84. Furthermore, as with the system 174,the coil 84 and magnet 82 are aligned with the longitudinal axis 178 ofthe vibrating assembly 158, so the passage 172 is less obstructed.

Referring additionally now to FIG. 16, another electrical powergenerating system 184 is representatively illustrated. The system 184 isvery similar to the system 180 described above, except that multiplemagnets 82 are displaced by the vibrating assembly 158 relative torespective multiple ferromagnetic cores 182 positioned in respectivemultiple coils 84. Of course, the coils 84 and cores 182 could bedisplaced relative to the magnets 82 in keeping with the principles ofthe invention. One beneficial feature of the system 184 as compared tothe system 180 is that an increased level of electrical power isproduced by the multiple sets of magnets 82 and coils 84. Anotherbeneficial feature of the system 184 as compared to the system 180 is areduced magnetic reluctance of the magnetic circuit.

Referring additionally now to FIG. 17, another electrical powergenerating system 186 is representatively illustrated. The system 186 issimilar in many respects to the system 174 described above, and soelements depicted in FIG. 17 which are similar to those described aboveare indicated using the same reference numbers. The system 186 may beused for the system 18 in the well 10 as illustrated in FIG. 1, or itmay be used in other applications.

The system 186 differs from the other systems described above in onerespect in that a magnet 82 and coils 84 included in a generator 188 ofthe system are enclosed within a housing 190 attached to the arm 74. Themagnet 82 is movably supported within the coils 84 by biasing devices192 positioned between the housing 190 and each end of the magnet. Asthe vibrating assembly 158 displaces in response to the fluid flow 32,the housing 190 will also displace back and forth, causing the mass ofthe magnet 82 to alternately compress the biasing devices 192, andthereby permitting the magnet to displace relative to the coils 84.

The biasing devices 192 are representatively illustrated in FIG. 17 asbeing compression springs, but it should be clearly understood thatother types of biasing devices may be used to movably support the magnet82. For example, elastomeric stoppers, compressed fluid, magnets havingpoles which repel poles of the magnet 82, etc. may be used to bias themagnet toward a neutral position relative to the coils 84.Alternatively, the magnet 82 could displace relative to the coils 84without use of any biasing device.

The housing 190 prevents the fluid flow 32 and any debris fromcontacting the magnet 82 and coils 84. The interior of the housing 190could be at atmospheric or another pressure (e.g., by sealing air or agas within the housing), or it could be pressure balanced with respectto the passage 172.

In the system 186, and in the other systems described herein whichutilize a magnet and coil to produce electricity, it may be beneficialto be able to initiate displacement of the vibrating assembly using themagnet and coil. In this manner, displacement of the vibrating assemblycould be initiated at lower rates of the fluid flow 32. For example, inthe system 186, an electric potential could be applied to one or both ofthe coils 84 to generate a magnetic field which would cause the magnet82 to displace relative to the coils. This displacement of the magnet 82relative to the coils 84 would compress one of the biasing devices 192,thereby causing the arm 74 to displace in response. Once the arm 74 isdisplaced away from its neutral position, the elastic support 78 willbias the arm back toward the neutral position and, thus, displacement ofthe vibrating assembly 158 will be initiated. Once the displacement 80is initiated, the vortices shed by the vortex shedding device 72 due tothe fluid flow 32 will continue to displace the assembly 158 back andforth.

Referring additionally now to FIG. 18, another electrical powergenerating system 194 is representatively illustrated. The system 194 issimilar in many respects to the system 186 described above, and soelements depicted in FIG. 18 which are similar to those described aboveare indicated using the same reference numbers. The system 194 may beused for the system 18 in the well 10 as illustrated in FIG. 1, or itmay be used in other applications.

The system 194 has a generator 196 which includes the magnet 82 and coil84 positioned within the housing 190. However, the housing 190 issubstantially rigidly mounted relative to the vibrating assembly 158,instead of being attached to the arm 74 as in the system 186. Inaddition, no biasing device is used in the housing 190 to support themagnet 82 relative to the coil 84.

The magnet 82 is displaced relative to the coil 84 by another magnet198, which is attached to the arm 74. The magnet 198 displaces with thearm 74 when the assembly 158 vibrates in response to the fluid flow 32.The magnet 198 is configured and positioned relative to the magnet 82 sothat corresponding poles of the magnets repel each other. Thus, when themagnet 198 displaces, the repelling forces between the poles of themagnets 82, 198 bias the magnet 82 to displace along with the magnet198. Displacement of the magnet 82 relative to the coil 84 causeselectricity to be produced in the coil.

As described above, an electric potential may be applied to the coil 84to initiate displacement of the vibrating assembly 158. In this case,the electric potential applied to the coil 84 will cause the magnet 82to displace relative to the coil. Displacement of the magnet 82 willcause a corresponding displacement of the magnet 198, due to therepelling forces between corresponding poles of the magnets. Thisdisplacement of the magnet 198 initiates displacement of the vibratingassembly 158, which will continue to displace back and forth due to thevortices shed by the vortex shedding device 72 in response to the fluidflow 32.

Referring additionally now to FIG. 19, another electrical powergenerating system 200 is representatively illustrated. Elements of thesystem 200 which are similar those previously described are indicated inFIG. 19 using the same reference numbers. The system 200 may be used forthe system 18 in the well 10 as illustrated in FIG. 1, or it may be usedin other applications.

The system 200 differs in one respect from the other systems describedabove, in that it includes a generator 202 in which relative rotationaldisplacement between a magnet 204 and coils 206 is used to produceelectricity in the coils. The magnet 204 may actually be made up ofmultiple individual magnets.

As in the other systems described above, the system 200 has a vibratingassembly 210 which includes the vortex shedding device 72 attached to anarm 208. Vortices shed by the device 72 in response to the fluid flow 32cause the arm 208 to displace back and forth (as indicated by the arrows80).

A housing 212 of the generator 202 encloses the magnet 204 and coils206. The housing 212 is attached to the arm 208 and to the elasticsupport 78. As the arm 208 displaces back and forth, the elastic support78 flexes and rotational displacement (indicated by arrows 214) of thehousing 212 is produced.

The coils 206 are attached to, and rotate with, the housing 212.Rotation of the coils 206 relative to the magnet 204 causes electricityto be produced in the coils 206. Of course, the magnet 204 could beattached to the housing 212 for rotation relative to the coils 206 inkeeping with the principles of the invention.

Preferably, the housing 212 is positioned at or near a center ofrotation of the vibrating assembly 210. This reduces the rotationalinertia of the generator 202, permitting the assembly 210 to vibrate atlower rates of the fluid flow 32. Note that an electric potential may beapplied to one or both of the coils 206 to initiate the rotationaldisplacement 214 of the housing 212 and thereby initiate vibratingdisplacement 80 of the assembly 210.

Referring additionally now to FIG. 20, a magnet configuration 216 isrepresentatively illustrated. The magnet configuration 216 may be usedin any of the systems described herein which utilize one or more magnetsin a generator to produce electricity. It should be clearly understoodthat any type of magnet (permanent magnet, electromagnet, combinationsof magnets and ferromagnetic material etc.), any number of magnets, andany configurations of magnets may be used in the systems describedherein, in keeping with the principles of the invention.

The magnet configuration 216 depicted in FIG. 20 uses two permanentmagnets 218 separated by a ferromagnetic spacer 220. The spacer 220directs and concentrates a magnetic field 222 produced by the magnets218. Note that similar poles of the magnets 218 (the “S” or south polesof the magnets as depicted in FIG. 20) are each positioned proximate thespacer 220. Additional magnets 218 and spacers 220 may be used ifdesired to produce a magnetic field 222 having an even higher density.

Note that the spacer 220 is not necessary to produce an increasedmagnetic flux density, since merely positioning the similar poles of themagnets 218 proximate each other will increase the magnetic flux densitygenerated by the magnets. The spacer 220 could be made of metals otherthan ferromagnetic materials, and the spacer 220 could instead be anadhesive, elastomer, etc.

Referring additionally now to FIG. 21, another electrical powergenerating system 224 is representatively illustrated. The system 224 issimilar in many respects to systems described above, and so elements ofthe system which are similar to those previously described are indicatedin FIG. 21 using the same reference numbers. The system 224 may be usedfor the system 18 in the well 10 as illustrated in FIG. 1, or it may beused in other applications.

The system 224 differs in one respect from the other systems describedabove in that it does not use a vortex shedding device to producevortices having a frequency related to a resonant frequency of avibrating assembly. Instead, the system 224 uses alternating liftcoefficients produced by a lift reversal device 226 attached to the arm74 in a vibrating assembly 228 in order to induce the vibratingdisplacement 80 of the assembly.

As depicted in FIG. 21, the lift reversal device 226 is preferably arectangular prism-shaped device attached at an upstream end of the arm74. The lift coefficient (l) produced by the device 226 is dependentupon an angle of attack (α) of the device relative to the fluid flow 32.FIG. 22 depicts with a solid line 228 a plot of the lift coefficientversus angle of attack for the lift reversal device 226.

As can be seen from the plot 228, the lift coefficient increasesrelatively rapidly as the angle of attack increases from zero. However,the lift coefficient eventually reaches a maximum positive value 230, atwhich point a further increase in the angle of attack begins to reducethe lift coefficient. Still further increases in the angle of attackwill eventually cause the lift coefficient to return to zero, at whichpoint 232 a further increase in the angle of attack will cause the liftcoefficient to go negative. The lift coefficient eventually reaches amaximum negative value 234, at which point a further increase in theangle of attack again increases the lift coefficient.

The plot 228 may be compared to a dashed line plot 236 of liftcoefficient versus angle of attack for a conventional airfoil (notshown). Note that lift reversal does not occur for the airfoil. Instead,the lift coefficient initially increases with increased angle of attack,but then the increase in lift coefficient gradually diminishes, untilboundary layer separation occurs. Thus, an airfoil shape would not bepreferred for the lift reversal device 226.

The lift reversal produced by the lift reversal device 226 in responseto the fluid flow 32 is used in the system 224 to produce back and forthvibrating displacement 80 of the vibrating assembly 228. As the liftcoefficient increases, the arm 74 is increasingly biased to deflect in afirst direction away from its neutral position. Increased deflection ofthe arm 74 increases the angle of attack of the lift reversal device 226relative to the fluid flow 32, thereby initially further increasing thelift coefficient. Eventually (with increased angle of attack), the liftcoefficient begins to decrease and returns to zero, at which point thearm 74 is no longer biased in the first direction, and the elasticsupport 78 returns the arm to and beyond its neutral position.

The angle of attack then goes negative, the lift coefficient againincreases, and the arm 74 is increasingly biased to deflect in anopposite second direction away from its neutral position. Eventually(with increased angle of attack), the lift coefficient begins todecrease and again returns to zero, at which point the arm 74 is nolonger biased in the second direction, and the elastic support 78 againreturns the arm to and beyond its neutral position. This process isrepeated over and over, thereby producing the vibrating displacement 80of the vibrating assembly 228.

This vibrating displacement 80 is used by the generator 30 to produceelectricity. The generator 30 may be any type of electrical powergenerator which is capable of producing electricity from thedisplacement 80, including any of the generators described herein.

The angle of attack (α) of the lift reversal device 226 relative to thefluid flow 32 may be part of the system 224 configuration as initiallyinstalled. Alternatively, the angle of attack may be initiated byproducing an initial deflection of the arm 74 after installation of thesystem 224 and after the fluid flow 32 has been initiated. For example,if the generator 30 includes a magnet and coil, an electric potentialmay be applied to the coil to produce a displacement of the magnetrelative to the coil, thereby producing a displacement of the arm 74, asdescribed above. As another example, if the generator includes anelectromagnetically active element, an electric potential or magneticfield may be applied to the element to produce strain in the element,thereby producing a displacement of the arm 74, as also described about.As yet another example, a flow diverter, such as the diverter 152depicted in FIG, 12, may be used to divert the fluid flow 32 so that itimpinges on the lift reversal device 226 at a nonzero angle relative tothe passage 172. Any means of producing an initial angle of attack ofthe lift reversal device 226 relative to the fluid flow 32 may be usedin keeping with the principles of the invention.

Referring additionally now to FIG. 23, another electrical powergenerating system 238 is representatively illustrated. The system 238 issimilar in some respects to other systems described above, and soelements depicted in FIG. 23 which are similar to those previouslydescribed are indicated using the same reference numbers. The system 238may be used for the system 18 in the well 10 depicted in FIG. 1, or itmay be used in other applications.

The system 238 includes the vortex shedding device 72 which produces theback and forth displacement 80 in response to the fluid flow 32 throughthe passage 172 formed through the housing 170. However, the vortexshedding device 72 is attached to an upstream end of an arm 240 which issecured via a pivot 242 to the housing 170. The arm 240 and device 72are included in a vibrating assembly 254 of the system 238.

The pivot 242 serves to support the arm 240, but preferably does notbias the arm toward a neutral position. Instead, the arm 240 is biasedtoward its neutral position by a membrane 244. The membrane 244 includesa relatively rigid portion 246 and a relatively flexible portion 248.The arm 240 is preferably attached to the rigid portion 246 of themembrane 244.

The membrane 244 performs at least two important functions in the system238. First, the membrane 244 serves as at least a portion of an elasticsupport 256 for the arm 240, in that the flexible portion 248 helps tobias the arm toward a neutral position. Second, the membrane 244 servesto isolate at least a portion of a generator 250 from the fluid flow 32in the passage 172. The generator 250 is depicted in FIG. 23 as beingpositioned in a recess 252 formed in a sidewall of the housing 170, withthe membrane 244 isolating the recess from the passage 172.

The generator 250 is also depicted in FIG. 23 as including the stack ofelectromagnetically active elements 168. However, it should be clearlyunderstood that any type of generator capable of transforming thedisplacement 80 into electrical power may be used, including any of thevarious generators described herein, in keeping with the principles ofthe invention. Note that the elements 168 may also be considered part ofthe support for the arm 240, since their elasticity (or lack thereof)will influence how the vibrating assembly 254 responds to the fluid flow32.

In operation, the fluid flow 32 causes the device 72 to shed vortices(not shown) at a resonant frequency of the vibrating assembly 254. Thisproduces the back and forth lateral displacement 80 of the arm 240 atthe device 72, which rotates the arm about the pivot 242. At theattachment between the arm 240 and the membrane 244, the displacement 80is again substantially laterally directed.

The displacement 80 is transmitted via the membrane 244 to the elements168, thereby producing strain in the elements. The displacement 80 isaxially directed relative to the elements 168, thereby producing axialstrain in the elements. This strain in the elements 168 produceselectricity directly from the elements (e.g., if the elements are madeof a piezoelectric or electrostrictive material) or a magnetic field(e.g., if the elements are made of a magnetostrictive material). If amagnetic field is produced by strain in the elements 168, then thegenerator 250 may also include a coil (not shown) in which electricityis produced in response to the magnetic field.

Note that displacement of the arm 240 may be initiated by applying anelectric potential or magnetic field to the elements 168, therebyproducing strain in the elements and deflecting the membrane 244. Thisinitial displacement of the arm 240 may be used to initiate thevibrating displacement 80 of the assembly 254 in response to the fluidflow 32.

Referring additionally now to FIG. 24, another electrical powergenerating system 260 is representatively illustrated. The system 260may be used for the system 18 in the well 10 depicted in FIG. 1, or itmay be used in other applications.

The system 260 includes a vortex shedding device 262 attached at anupstream end of an elongated beam 264. An opposite end of the beam 264is rigidly mounted.

An electromagnetically active material 266 is attached to opposinglateral sides of the beam 264. As fluid flow (indicated by arrows 268)impinges on the vortex shedding device 262, the device sheds vortices(not shown in FIG. 24, see vortices 34 depicted in FIG. 3) which producealternating lift forces on the device and beam 264. These lift forcesproduce back and forth vibrating displacement (indicated by arrows 270)of the free end of the beam 264, thereby producing alternating strain inthe beam.

Preferably, the vortex shedding device 262 sheds the vortices 34 at afrequency which is substantially equal to a resonant frequency of avibrating assembly 272 of the system 260. The vibrating assembly 272 asdepicted in FIG. 24 includes the beam 264, the vortex shedding deviceand the material 266. Other elements which influence the resonantfrequency of the assembly 272 may be included in the assembly.

The system 260 is preferably configured so that, for a range of expectedvelocities of the fluid flow 268, the lock-in phenomenon will occur asrepresented by the substantially horizontal portion 64 of the graphdepicted in FIG. 5 and described above. That is, the vortex sheddingfrequency (f) will remain substantially constant at the resonantfrequency of the assembly 272. This will enhance the amplitude of thedisplacement 270, thereby increasing the strain in the beam 264, andthus increasing the strain imparted to the material 266.

If the material 266 is a piezoelectric or electrostrictive material, thestrain imparted to the material will produce electricity in thematerial. If the material 266 is a magnetostrictive material, the strainimparted to the material will produce a magnetic field, which may beused to produce electricity in a coil (not shown). Thus, the material266 coupled to the vibrating beam 264 may be considered a generator 274of the system 260.

In addition to being used to generate electricity, the system 260 mayalso be used as a sensor to detect the velocity of the fluid flow 268.It is believed that the amplitude of the displacement 270 (and thus thestrain in the beam 264 and the electrical energy output by the material266) will be proportional to the velocity of the fluid flow 268.Therefore, by measuring the electrical energy output by the material266, an indication is given of the velocity of the fluid flow 268.

Note that it is not necessary for the beam 264 to have the shapedepicted in FIG. 24. A similar system 280 representatively illustratedin FIG. 25 includes a beam 282 with a nonuniform shape (e.g., a taperedshape). In order to prevent over-straining the material 266, or toprovide more energy into the electromagnetically active material, it isattached to a relatively thicker portion 284 of the beam 282 near therigidly mounted end of the beam. Variations in the shape of the beam 282may also be used to modify the resonant frequency of a vibratingassembly 286 of the system 280, so that it will match a frequency ofvortices shed by the device 262 at expected fluid flow velocities, tomatch the frequencies of vortices shed by the device 262 at a widerrange of fluid flow velocities, or for other reasons. The shape of thebeam 282 may provide a-better mechanical impedance match with thefluid-induced vibrations.

It is also not necessary for the material 266 to have a uniformthickness on the beam 264 in the system 260, or on the beam 282 in thesystem 280. It will be appreciated by one skilled in the art that thereis increased strain energy produced in the rigidly mounted end 276 ofthe beam 264 as compared to the free end 278 of the beam 264 in thesystem 260, and that there is increased strain energy produced in therigidly mounted end 288 of the beam 282 as compared to the free end 290of the beam 282 in the system 280. Representatively illustrated in FIGS.26 & 27 are alternate configurations of the systems 260, 280,respectively, in which an increased thickness of the material 266 isused near the rigidly mounted end 276 of the beam 264 and near therigidly mounted end 288 of the beam 282.

In FIG. 26, the material 266 is provided in a single layer, and thethickness of the layer progressively increases toward the rigidlymounted end 276. In FIG. 27, the material 266 is provided in multiplelayers, with the number of layers progressively increasing toward therigidly mounted end 288. The increased material 266 thickness in each ofthe systems 260, 280 as depicted in FIGS. 26 & 27 allows the material tomore effectively utilize the increased strain energy present at therespective rigidly mounted end 276, 288. Note that the multiple layeredmaterial 266 (as depicted in FIG. 27) could be used in the system 260,and the tapered thickness of the material (as depicted in FIG. 26) couldbe used in the system 280. In addition, any other means of providingincreased volume of the material 266 at a region of increased strainenergy may be used in keeping with the principles of the invention.

As noted above, the various electrical power generating systemsdescribed herein may be used in applications other than in subterraneanwells. For example, the flow of air across a wing of an airplane couldbe used to generate electricity using the systems described herein. Ifthe electrical power generated by the system is proportional, orotherwise related, to the velocity of the air, then the system may alsobe used as an air speed sensor for the airplane. It is to be clearlyunderstood that the applications of the principles described herein arenot limited in any manner to the specific embodiments contained in thisdescription.

Of course, a person skilled in the art would, upon a carefulconsideration of the above description of representative embodiments ofthe invention, readily appreciate that many modifications, additions,substitutions, deletions, and other changes may be made to thesespecific embodiments, and such changes are contemplated by theprinciples of the present invention. For example, any of the electricalpower generating systems described herein may include any of thegenerators, vibrating assemblies, elastic supports, lift reversaldevices or vortex shedding devices described herein, or any combinationof the generators, vibrating assemblies, elastic supports, lift reversaldevices or vortex shedding devices described herein. Accordingly, theforegoing detailed description is to be clearly understood as beinggiven by way of illustration and example only, the spirit and scope ofthe present invention being limited solely by the appended claims andtheir equivalents.

1. An electrical power generating system, comprising: a vibrating assembly including a vortex shedding device which sheds vortices in response to fluid flow across the vibrating assembly; and a generator which generates electrical power in response to vibration of the vibrating assembly, wherein the vortex shedding device sheds the vortices at a frequency which is substantially equal to a resonant frequency of the vibrating assembly.
 2. The system according to claim 1, wherein the vibrating assembly further includes an elastic support for the vortex shedding device, the elastic support biasing the vortex shedding device toward a neutral position against lift forces produced by the vortices.
 3. The system according to claim 1, wherein the vortices produce alternating lift forces on the vibrating assembly, thereby causing the vibrating assembly to vibrate.
 4. The system according to claim 1, wherein the generator includes at least one magnet which is displaced relative to a coil in response to vibration of the vibrating assembly.
 5. The system according to claim 1, further comprising a substantially rigid arm connecting the vortex shedding device to the generator, and wherein an elastic support supports the arm between the vortex shedding device and the generator.
 6. The system according to claim 1, further comprising a tubular string having a flow passage formed therethrough, and wherein the vortex shedding device is positioned in a recess internally formed in the tubular string, the recess being laterally offset from the flow passage and in fluid communication with the flow passage.
 7. The system according to claim 1, wherein the vibrating assembly and the generator are positioned in a weilbore of a well.
 8. An electrical power generating system, comprising: a vibrating assembly including a vortex shedding device which sheds vortices in response to fluid flow across the vibrating assembly; and a generator which generates electrical power in response to vibration of the vibrating assembly, wherein the vortex shedding device sheds the vortices at a frequency which is substantially equal to a resonant frequency of the vibrating assembly, and wherein the generator includes an electromagnetically active material in which strain is induced in response to vibration of the vibrating assembly.
 9. The system according to claim 8, wherein motion of the vibrating assembly is transmitted to the electromagnetically active material via a leveraging mechanism which decreases an amplitude of the motion.
 10. The system according to claim 9, wherein the leveraging mechanism elastically supports the vortex shedding device, thereby influencing the resonant frequency of the vibrating assembly.
 11. An electrical power generating system, comprising: a vibrating assembly including a vortex shedding device which sheds vortices in response to fluid flow across the vibrating assembly; and a generator which generates electrical power in response to vibration of the vibrating assembly, wherein the vortex shedding device sheds the vortices at a frequency which is substantially equal to a resonant frequency of the vibrating assembly, and wherein the generator includes an electromagnetically active material attached to a beam of the vibrating assembly, so that strain in the beam is transmitted to the material, and electricity is produced in response to the strain in the material.
 12. An electrical power generating system, comprising: an elongated arm; a vortex shedding device; an electrical power generator which generates electrical power in response to displacement of the arm; and an elastic support which supports the arm against alternating lift forces produced by vortices shed by the vortex shedding device, the elastic support being less rigid than the arm.
 13. The system according to claim 12, wherein the arm vibrates at a resonant frequency in response to the alternating lift forces.
 14. The system according to claim 13, wherein a frequency of the vortices shed by the vortex shedding device is substantially equal to the resonant frequency.
 15. The system according to claim 12, wherein the generator includes at least one magnet and at least one coil, relative displacement between the coil and magnet producing electricity in response to vibration of the arm.
 16. The system according to claim 15, wherein the generator includes at least two of the magnets and at least two of the coils, at least one of the magnets and at least one of the coils being positioned on each of opposite lateral sides of the arm.
 17. The system according to claim 12, wherein the vortex shedding device is positioned in a recess laterally offset from a flow passage.
 18. The system according to claim 17, wherein the recess is in fluid communication with the flow passage.
 19. The system according to claim 17, further comprising a flow diverter positioned in the recess.
 20. The system according to claim 19, wherein the flow diverter increases a velocity of fluid impinging on the vortex shedding device in the recess.
 21. The system according to claim 19, wherein the flow diverter causes fluid flowing through the recess to impinge on the vortex shedding device at an angle relative to a longitudinal axis of the passage, the angle being substantially greater than zero.
 22. The system according to claim 21, wherein the angle is approximately 20 degrees to approximately 60 degrees.
 23. The system according to claim 17, wherein the flow passage is formed through a tubular string.
 24. The system according to claim 23, wherein the tubular string is positioned in a wellbore.
 25. The system according to claim 17, wherein a flow diverter influences fluid in the passage to flow toward the recess.
 26. The system according to claim 25, wherein the flow diverter includes at least one projection extending into the passage opposite the recess.
 27. The system according to claim 25, wherein the flow diverter includes at least one vane positioned in the passage.
 28. The system according to claim 27, wherein the vane is rotatably mounted relative to the passage.
 29. The system according to claim 28, further comprising a biasing device which biases the vane to restrict flow through the passage, thereby diverting flow toward the recess.
 30. The system according to claim 12, wherein the arm is substantially rigid.
 31. The system according to claim 12, wherein the elastic support supports the arm between the vortex shedding device and the generator.
 32. The system according to claim 12, wherein the vortex shedding device sheds the vortices in response to fluid flow through a flow passage, and wherein the arm vibrates at a resonant frequency which is substantially equal to a frequency of the vortices over a predetermined range of velocity of the fluid flow.
 33. The system according to claim 12, wherein the vortex shedding device is positioned in a channel laterally offset from a flow passage extending through the system.
 34. The system according to claim 33, wherein the channel has opposite ends each of which is in fluid communication with the flow passage.
 35. The system according to claim 34, wherein the channel is isolated from the flow passage between the opposite ends of the channel.
 36. The system according to claim 33, further comprising a flow diverter positioned in the channel.
 37. The system according to claim 36, wherein the flow diverter increases a velocity of fluid impinging on the vortex shedding device in the channel.
 38. The system according to claim 36, wherein the flow diverter causes fluid flowing through the channel to impinge on the vortex shedding device at an angle relative to a longitudinal axis of the passage, the angle being substantially greater than zero.
 39. The system according to claim 38, wherein the angle is from approximately 20 degrees to approximately 60 degrees.
 40. The system according to claim 33, wherein the flow passage is formed through a tubular string.
 41. The system according to claim 40, wherein the tubular string is positioned in a wellbore.
 42. The system according to claim 33, wherein a flow diverter influences fluid in the passage to flow toward the channel.
 43. The system according to claim 42, wherein the flow diverter includes at least one projection extending into the passage opposite the channel.
 44. The system according to claim 42, wherein the flow diverter includes at least one vane positioned in the passage.
 45. The system according to claim 44, wherein the vane is rotatably mounted relative to the passage.
 46. The system according to claim 45, further comprising a biasing device which biases the vane to restrict flow through the passage, thereby diverting flow toward the recess.
 47. The system according to claim 12, wherein the arm is substantially more rigid than the elastic support.
 48. The system according to claim 12, wherein fluid flow impinges on the vortex shedding device at a greater velocity than the fluid flow impinges on the arm.
 49. The system according to claim 12, wherein the vortices impinge on at least one surface area attached to the arm to thereby produce the alternating lift forces.
 50. The system according to claim 49, wherein the surface area is formed on the vortex shedding device downstream of a portion of the vortex shedding device at which the vortices are shed.
 51. The system according to claim 12, further comprising a flow diverter which increases a velocity of fluid impinging on the vortex shedding device.
 52. The system according to claim 12, further comprising a flow diverter which causes fluid flowing through the system to impinge on the vortex shedding device at an angle substantially greater than zero.
 53. The system according to claim 52, wherein the angle is from approximately 20 degrees to approximately 60 degrees.
 54. The system according to claim 12, wherein the generator includes at least first and second magnets which displace in opposite directions relative to respective first and second coils in response to displacement of the arm.
 55. The system according to claim 12, wherein the generator includes a first magnet which displaces in a first direction relative to a first coil while a second magnet displaces in a second direction relative to a second coil when the arm displaces, the first direction being opposite to the second direction.
 56. The system according to claim 12, wherein the system is positioned in a wellbore of a subterranean well.
 57. An electrical power generating system, comprising: an elongated arm; a vortex shedding device; an electrical power generator which generates electrical power in response to displacement of the arm; and an elastic support which supports the arm against alternating lift forces produced by vortices shed by the vortex shedding device, and wherein the generator includes an electromagnetically active material in which strain is induced when the arm vibrates.
 58. The system according to claim 57, wherein the generator further includes a leveraging mechanism which reduces a displacement amplitude of the arm, and which applies the reduced amplitude to the electromagnetically active material.
 59. The system according to claim 58, wherein the leveraging mechanism includes an integrally formed lever device having multiple flexure pivots formed thereon.
 60. The system according to claim 58, wherein the leveraging mechanism and the electromagnetically active material form portions of the elastic support. 